CDK4 and breast carcinoma: Advances in PROteolysis TArgeting Chimeras (PROTACs) suppressing CDK4/6 were recently introduced in breast cancer and glioblastoma cell lines, where CDK4 and CDK6 protein expressions were reduced considerably.46 Thus, a PROTAC targeting CDK4/6 could be used as an alternative to PaRi, if resistance to these drugs might be an issue.